It seems as though Java 9 is just not ready yet. They would rather have better quality which is a good approach. Enterprises are just not ready for Java 9 (or Java 8).
http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-September/004887.html
http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-September/004887.html